Pilot signals

ABSTRACT

A first terminal receives, on a radio link of a cellular network, at least one uplink pilot signal transmitted by at least one second terminal The first terminal transmits, on the radio link and to an access node of the cellular network, an uplink report message indicative of at least one property of the received at least one uplink pilot signal.

TECHNICAL FIELD

Various embodiments relate to communicating pilot signals on the radiolink of a cellular network and to corresponding devices.

BACKGROUND

Pilot signals—sometimes also referred to as reference signals—aretypically used for determining the condition of a channel implemented ona radio link of a cellular network (channel sensing). Channel sensingmay comprise channel estimation and channel measurements. In referenceimplementations, pilot signals are reoccurring communicated in order toconsider time-dependencies of the channel condition, e.g., due totime-varying multipath effects or Doppler spread. The pilot signals aretransmitted having well-defined transmit parameters such as amplitudeand phase. From the received pilot signals and based on knowledge of thetransmit parameters, it is then possible to deduce properties of theradio link between transmitter and receiver and conclude on acorresponding condition of the channel. Examples of uplink (UL) pilotsignals are described for the Third Generation Partnership Project(3GPP) Long Term Evolution (LTE) radio access technology (RAT) in 3GPPTechnical Specification (TS) 36.211 V.13.0.0 (2015-12) 5.5; examples ofdownlink (DL) pilot signals are described for the 3GPP LTE RAT in 3GPPTS 36.211 V.13.0.0 (2015-12) 6.10.

The amplitude with which pilot signals are transmitted defines atransmit power. Tailoring the transmit power can impose certainchallenges. Typically, a tradeoff situation exists between increasedinterference (for large transmit powers) and inaccuracies of channelsensing (for small transmit power).

SUMMARY

Thus, a need for advanced techniques of communicating pilot signals on aradio link exists. This need is met by the features of the independentclaims. The dependent claims define embodiments.

According to an example, a method comprises a first terminal receiving,on a radio link of a cellular network, at least one uplink pilot signal.The at least one uplink pilot signal is transmitted by at least onesecond terminal. The method further comprises the first terminaltransmitting, on the radio link and to an access node of the cellularnetwork, an uplink report message. The uplink report message isindicative of at least one property of the received at least one uplinkpilot signal.

According to an example, a method comprises an access node receiving anuplink report message indicative of at least one property of at leastone uplink pilot signal. The access node receives the uplink reportmessage on a radio link of a cellular network and from a first terminal.The uplink pilot signal is received by the first terminal. The at leastone uplink pilot signal being transmitted by at least one secondterminal.

According to an example, a terminal attachable to a cellular networkcomprises an interface. The interface is configured to transceive on aradio link of the cellular network. The terminal further comprises atleast one processor. The at least one processor is configured toreceive, via the interface, at least one uplink pilot signal. The uplinkpilot signal is transmitted by at least one further terminal. The atleast one processor is further configured to transmit, via the interfaceand to an access node of the cellular network, and uplink reportmessage. The uplink report message is indicative of at least oneproperty of the received at least one uplink pilot signal.

According to an example, an access node of a cellular network comprisesan interface. The interface is configured to transceive on a radio linkof the cellular network. The access node further comprises at least oneprocessor. The at least one processor is configured to receive, via theinterface and from a first terminal, and uplink report message. Theuplink report message is indicative of at least one property of at leastone uplink pilot signal received by the first terminal. The at least oneuplink pilot signal is transmitted by at least one second terminal.

According to an example, a computer program product is provided. Thecomputer program product comprises program code executable by at leastone processor. Executing the program code causes the at least oneprocessor to perform a method. The method comprises a first terminalreceiving, on a radio link of a cellular network, at least one uplinkpilot signal. The at least one uplink pilot signal is transmitted by atleast one second terminal. The method further comprises the firstterminal transmitting, on the radio link and to an access node of thecellular network, an uplink report message. The uplink report message isindicative of at least one property of the received at least one uplinkpilot signal.

According to an example, a computer program product is provided. Thecomputer program product comprises program code executable by at leastone processor. Executing the program code causes the at least oneprocessor to perform a method. The method comprises an access nodereceiving an uplink report message indicative of at least one propertyof at least one uplink pilot signal. The access node receives the uplinkreport message on a radio link of a cellular network and from a firstterminal. The uplink pilot signal is received by the first terminal. Theat least one uplink pilot signal being transmitted by at least onesecond terminal.

According to an example, a method comprises, in a first subset of asequence of transmission intervals: communicating, on the radio link ofa cellular network and according to a resource mapping, pilot signalshaving a non-zero first transmit power. The method further comprises, inthe second subset of the sequence of transmission intervals:communicating, on the radio link and according to the resource mapping,the pilot signals having a non-zero second transmit power. The secondtransmit power is larger than the first transmit power.

According to an example, a device comprises an interface. The interfaceis configured to transceive on a radio link of a cellular network. Thedevice further comprises at least one processor. The at least oneprocessor is configured to communicate, on a radio link of the cellularnetwork and according to a resource mapping, pilot signals having anon-zero first transmit power in a first subset of a sequence oftransmission intervals. The at least one processor is further configuredto communicate, on the radio link and according to the resource mapping,the pilot signals having a non-zero second transmit power which islarger than the first transmit power in a second subset of the sequenceof transmission intervals.

According to an example, a computer program product is provided. Thecomputer program product comprises program code executable by at leastone processor. Executing the program code causes the at least oneprocessor to perform a method. The method comprises, in a first subsetof a sequence of transmission intervals: communicating, on the radiolink of a cellular network and according to a resource mapping, pilotsignals having a non-zero first transmit power. The method furthercomprises, in the second subset of the sequence of transmissionintervals: communicating, on the radio link and according to theresource mapping, the pilot signals having a non-zero second transmitpower. The second transmit power is larger than the first transmitpower.

According to an example a method comprises a first device receiving, ona radio link of a cellular network, at least one uplink or downlinkpilot signal transmitted by at least one second device. The methodfurther comprises the first device transmitting, on the radio link andto an access node of the cellular network, a report message indicativeof at least one property of the received at least one uplink or downlinkpilot signal.

According to an example a method comprises an access node of a cellularnetwork receiving, on a radio link of the cellular network and from afirst device, a report message indicative of at least one property of atleast one uplink or downlink pilot signal received by the first device,the at least one uplink or downlink pilot signal being transmitted by atleast one second device.

According to an example, a device comprises: an interface configured totransceive on a radio link of the cellular network; at least oneprocessor configured to receive, via the interface, at least one uplinkor downlink pilot signal transmitted by at least one further device,wherein the at least one processor is further configured to transmit,via the interface and to an access node of the cellular network, areport message indicative of at least one property of the received atleast one uplink or downlink pilot signal.

According to an example, an access node of a cellular network comprises:an interface configured to transceive on a radio link of the cellularnetwork, at least one processor configured to receive, via the interfaceand from a first device, a report message indicative of at least oneproperty of at least one uplink or downlink pilot signal received by thefirst device, the at least one uplink or downlink pilot signal beingtransmitted by at least one second device.

It is to be understood that the features mentioned above and those yetto be explained below may be used not only in the respectivecombinations indicated, but also in other combinations or in isolationwithout departing from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a cellular network according tovarious embodiments.

FIG. 2 is a schematic illustration of channels implemented on a radiolink of the cellular network according to various embodiments.

FIG. 3 is a schematic illustration of a repetitive resource mapping forpilot signals communicated in a sequence of transmission intervalsaccording to various embodiments, wherein the repetitive resourcemapping according to the embodiment of FIG. 3 employs frequency-divisionmultiple access in order to mitigate interference between multipleterminals communicating pilot signals.

FIG. 4 is a schematic illustration of repetitive resource mapping forpilot signals communicated in subsequent transmission intervalsaccording to various embodiments, wherein the repetitive resourcemapping according to the embodiment of FIG. 4 employs time-divisionmultiple access in order to mitigate interference between multipleterminals communicating pilot signals.

FIG. 5 is a schematic illustration of repetitions of a repetitiveresource mapping for pilot signals according to various embodiments.

FIG. 6 is a schematic illustration of repetitions of a repetitiveresource mapping for pilot signals according to various embodiments.

FIG. 7 schematically illustrates a first terminal receiving uplink pilotsignals transmitted by second terminals according to variousembodiments.

FIG. 8A is a signaling diagram illustrating a first terminal receivingan uplink pilot signal transmitted by a second terminal and furtherillustrating the first terminal transmitting an uplink report messageindicative of a property of the received uplink pilot signal accordingto various embodiments.

FIG. 8B is a signaling diagram illustrating a first terminal receivingan uplink pilot signal transmitted by a second terminal and furtherillustrating the first terminal transmitting an uplink report messageindicative of a property of the received uplink pilot signal accordingto various embodiments.

FIG. 9A is a signaling diagram illustrating a first terminal receiving aplurality of uplink pilot signals transmitted by a second terminal andfurther illustrating the first terminal transmitting an uplink reportmessage indicative of a property of the received plurality of uplinkpilot signals according to various embodiments.

FIG. 9B is a signaling diagram illustrating a first terminal receiving aplurality of uplink pilot signals transmitted by a second terminal andfurther illustrating the first terminal transmitting an uplink reportmessage indicative of a property of the received plurality of uplinkpilot signals according to various embodiments.

FIG. 10A is a signaling diagram illustrating a first terminal receivinga plurality of uplink pilot signals transmitted by a second terminal andfurther illustrating the first terminal transmitting an uplink reportmessage indicative of a property of the received plurality of uplinkpilot signals according to various embodiments, wherein in the scenarioof FIG. 10A the first terminal receives the uplink pilot signals duringsilent periods.

FIG. 10B is a signaling diagram illustrating a first terminal receivinga plurality of uplink pilot signals transmitted by a plurality of secondterminals and further illustrating the first terminal transmitting anuplink report message indicative of a property of the received pluralityof uplink pilot signals according to various embodiments.

FIG. 11A is a signaling diagram illustrating a first terminal receivingan uplink pilot signal transmitted by a second terminal, the firstterminal transmitting an uplink report message indicative of a propertyof the received uplink pilot signal, and further illustratingsporadically scheduling a respective transmission interval including theuplink pilot signal according to various embodiments.

FIG. 11B is a signaling diagram illustrating a first terminal receivingan uplink pilot signal transmitted by a second terminal, the firstterminal transmitting an uplink report message indicative of a propertyof the received uplink pilot signal, and further illustratingpersistently scheduling a respective transmission interval including theuplink pilot signal according to various embodiments.

FIG. 12 schematically illustrates communicating power-boosted pilotsignals according to various embodiments.

FIG. 13A schematically illustrates communicating, in a first subset of asequence of transmission intervals, pilot signals having a firsttransmit power and communicating, in a second subset of the sequence oftransmission intervals, communicating the pilot signals having a secondtransmit power which is larger than the first transmit power accordingto various embodiments.

FIG. 13B schematically illustrates the first transmit power and thesecond transmit power and further illustrates a factor by which thesecond transmit power is larger than the first transmit power accordingto various embodiments.

FIG. 14 schematically illustrates a time dependency of the factor bywhich the second transmit power is larger than the first transmit poweraccording to various embodiments.

FIG. 15 schematically illustrates a time dependency of the factor bywhich the second transmit power is larger than the first transmit poweraccording to various embodiments.

FIG. 16 schematically illustrates a time dependency of the factor bywhich the second transmit power is larger than the first transmit poweraccording to various embodiments.

FIG. 17 schematically illustrates a handover scenario according tovarious embodiments, wherein power-boosted uplink pilot signals areconsidered for the handover.

FIG. 18 schematically illustrates a handover scenario according tovarious embodiments, wherein power-boosted uplink pilot signals areconsidered for the handover.

FIG. 19 schematically illustrates a handover scenario according tovarious embodiments, wherein power-boosted uplink pilot signals areconsidered for the handover.

FIG. 20 is a signaling diagram illustrating persistently schedulingtransmission intervals of a second subset including the pilot signalshaving the second transmit power according to various embodiments.

FIG. 21 is a signaling diagram illustrating sporadically schedulingtransmission intervals of a second subset including the pilot signalshaving the second transmit power according to various embodiments.

FIG. 22 is a signaling diagram illustrating communicating a pilot signalin a transmission interval of a second subset and having a secondtransmit power, wherein the pilot signal is indicative of the secondtransmit power according to various embodiments.

FIG. 23 is a signaling diagram illustrating communicating a pilot signalin a transmission interval of a second subset and having a secondtransmit power and further illustrating communicating a control messagebeing indicative of the second transmit power according to variousembodiments.

FIG. 24 is a signaling diagram illustrating a handover scenarioaccording to various embodiments.

FIG. 25 is a signaling diagram illustrating scheduling, between twoaccess nodes of the cellular network, transmission intervals of a secondsubset including the pilot signals having a second transmit power largerthan a first transmit power according to various embodiments.

FIG. 26 schematically illustrates a terminal according to variousembodiments.

FIG. 27 schematically illustrates an access node according to variousembodiments.

FIG. 28 schematically illustrates a method according to variousembodiments.

FIG. 29 schematically illustrates a method according to variousembodiments.

FIG. 30 schematically illustrates a method according to variousembodiments.

FIG. 31 schematically illustrates a method according to variousembodiments.

FIG. 32 schematically illustrates a method according to variousembodiments.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following, embodiments of the invention will be described indetail with reference to the accompanying drawings. It is to beunderstood that the following description of embodiments is not to betaken in a limiting sense. The scope of the invention is not intended tobe limited by the embodiments described hereinafter or by the drawings,which are taken to be illustrative only.

The drawings are to be regarded as being schematic representations andelements illustrated in the drawings are not necessarily shown to scale.Rather, the various elements are represented such that their functionand general purpose become apparent to a person skilled in the art. Anyconnection or coupling between functional blocks, devices, components,or other physical or functional units shown in the drawings or describedherein may also be implemented by an indirect connection or coupling. Acoupling between components may also be established over a wirelessconnection. Functional blocks may be implemented in hardware, firmware,software, or a combination thereof.

Hereinafter, techniques of communicating pilot signals on a radio linkof a cellular network are described. The techniques may be applied touplink (UL) pilot signals communicated from a terminal to an accessnode. Alternatively or additionally, the techniques may be applied todownlink (DL) pilot signals communicated from the access node to theterminal. It is also possible, alternatively or additionally, to employthe techniques on pilot signals communicated in-between two terminalsfor device-to-device (D2D) communication, i.e., to sidelink pilotsignals or relay pilot signals.

Hereinafter, techniques are described which enable to flexibly tailortransmitting and/or receiving (communicating) of the pilot signals.Tailoring may relate to flexibly setting certain transmit properties ofthe pilot signals such as the amplitude. Tailoring may relate to a firstdevice flexibly receiving pilot signals which are intended for adifferent, second device and which are transmitted by a third device.

In some examples the techniques relate to dynamically adapting thetransmit power of pilot signals. In some examples, the transmit power ofpilot signals can be adjusted in-between two levels, three levels, ormore levels over the course of time. In some examples, the transmitpower of the pilot signals is boosted temporarily and occasionally to asecond transmit power which is higher than a baseline first transmitpower.

By dynamically adapting the transmit power, it is possible to enable alarger number of devices to receive the power-boosted pilot signal.Therefore, the larger number of devices such as further access nodesand/or terminals can benefit from the information derivable from thereceived pilot signal. E.g., channel sensing may be implemented at ahigh accuracy, because more information is available.

In some examples, the techniques relate to a first terminal receiving atleast one uplink pilot signal transmitted by at least one secondterminal. The at least one uplink pilot signal may be directedto/intended for an access node of the cellular network. Thus, the firstterminal may intercept this communication and receive the at least oneuplink pilot signal.

By receiving uplink pilot signals by the first terminal, it is possibleto gather additional information on the condition of channelsimplemented on the radio link. It may also be possible to performpositioning of the first terminal with respect to at least one of the atleast one second terminal and/or the access node.

In some examples, techniques are provided which enable toreduce/mitigate interference between multiple devices communicatingpilot signals. In some examples, interference is mitigated byorthogonally communicating pilot signals between the multiple devices.Orthogonality may be achieved by using time-division multiple access(TDMA), code-division multiple access (CDMA), and/or frequency-divisionmultiple access (FDMA). In some examples, inter-cell interference ismitigated by scheduling pilot signals across multiple cells. In someexamples, intra-cell and/or inter-cell interference is mitigated byappropriately setting the transmit power of pilot signals.

The techniques described herein may be applied to various use-cases,including the evolution of the existing LTE system and the nextgeneration of cellular network (e.g. New Radio (NR) access technologiesfor 5G cellular network). A particular use-case is a Multiple InputMultiple Output (MIMO) scenario, such as a Massive MIMO (MAMI) scenario.An initial phase of MAMI has just been developed in 3GPP as part of theLTE evolution and it is known as Full Dimension (FD)-MIMO. See 3GPP TS36.897. MAMI is commonly deployed by using Massive base-station antennasand a few terminal antennas with the main objective to obtain higherorder multi user MIMO. MAMI offers high spatial diversity. MIMO systemsmay use multiple transmit antennas and/or multiple receive antennas forcommunication on a radio link at an access node. MIMO enablesimplementation of coding techniques which use the temporal as well asthe spatial dimension for transmitting information. The coding providedin MIMO systems allows for considerable spectral efficiency and energyefficiency. A MAMI base station typically includes a comparably largenumber of antennas, e.g., several tens or even in excess of one hundredantennas with associated receiver circuitry. The extra antennas of theMAMI device allow radio energy to be spatially focused in transmissions;as well as a directional sensitive reception. Such techniques improvespectral efficiency and radiated energy efficiency. MAMI scenarios maybenefit from highly accurate channel sensing which becomes possible bythe techniques described herein.

FIG. 1 illustrates the architecture of a cellular network 100 accordingto some examples implementations. In particular, the cellular network100 according to the example of FIG. 1 implements the 3GPP LTEarchitecture, sometimes referred to as evolved packet system (EPS).This, however, is for exemplary purposes only. In particular, variousscenarios will be explained in the context of a radio link 101 betweenterminals 130-1, 130-2 and the cellular network 100 operating accordingto the 3GPP LTE architecture for illustrative purposes only. Similartechniques can be readily applied to various kinds of 3GPP-specifiedarchitectures, such as Global Systems for Mobile Communications (GSM),Wideband Code Division Multiplex (WCDMA), General Packet Radio Service(GPRS), Enhanced Data Rates for GSM Evolution (EDGE), Enhanced GPRS(EGPRS), Universal Mobile Telecommunications System (UMTS), and HighSpeed Packet Access (HSPA), and corresponding architectures ofassociated cellular networks.

Two terminals 130-1, 130-2 are connected via the radio link 101 to anaccess node 112 of the cellular network 100. The two terminals 130-1,130-2 may also be connected via the radio link 101 with each other (D2Dcommunication or sidelink communication). The access node 112 and theterminals 130-1, 130-2 implement the evolved UMTS terrestrial radioaccess technology (E-UTRAN); therefore, the access point node 112 is aneNB 112.

E.g., the terminals 130-1, 130-2 may be selected from the groupcomprising: a smartphone; a cellular phone; a tablet; a notebook; acomputer; a smart TV; a Machine Type Communication (MTC) device, anInternet-of-Things device; etc.

Communication on the radio link 101 can be in UL and/or DL direction, orD2D. Details of the radio link 101 are illustrated in FIG. 2. The radiolink 101 implements a plurality of channels 261-263. Radio resources 305associated with each channel 261-263. Each channel 261-263 comprises aplurality of resources 305 which are defined in time domain andfrequency domain. The resources 305 are typically structured byappropriate transmission intervals, e.g., in case of the LTE RAT intotime slots, subframes, frames, and radio frames (all not shown in FIG.2).

E.g., the resources 305 may correspond to individual symbols such asOrthogonal Frequency Division Multiplex (OFDM) symbols in 3GPP LTE RAT.E.g., the resources 305 may correspond to such individual resourceelements or a plurality of resources elements, sometimes referred to asresource blocks. Resource blocks comprise a plurality of sub-carriers.Thus, the resources may have different bandwidths depending on theparticular implementation, e.g., 15 kHz or 180 kHz.

Control channels 261, 262 may be associated with control messages. Thecontrol messages may configure operation of the terminals 130-1, 130-2,the eNB 112, and/or the radio link 101. E.g., radio resource control(RRC) messages and/or HARQ ACKs and NACKs can be exchanged via thecontrol channel. According to the E-UTRAN RAT, the control channels 261,262 may thus correspond to a Physical Downlink Control Channel (PDCCH)and/or a Physical Uplink Control Channel (PUCCH) and/or a PhysicalHybrid ARQ indicator Channel (PHICH).

Further, a shared channel 263 is associated with a payload messagescarrying higher-layer user-plane data packets associated with a givenservice implemented by the terminals 130-1, 130-2 and the eNB 112.According to the E-UTRAN RAT, the shared channel 263 may be a PhysicalDownlink Shared Channel (PDSCH) or a Physical Uplink Shared Channel(PUSCH). The shared channel 263 may sometimes also be used for sidelinkcommunication.

It is also possible to implement a relay channel. The relay channelallows communication of data between a first terminal 130-1, 130-2 andan eNB 112 via an intermediate relay. The intermediate relay may beimplemented by a second terminal 130-1, 130-2. See, e.g., 3GPP TechnicalReport (TR) 36.806 V.9.0.0 (2010-03). The various channels 261-263 canbe implemented using MIMO or MAMI techniques (MIMO channel). Here, byusing a plurality of transmit and/or receive antennas, spatial diversityis obtained.

Some resources 305 are used for communicating pilot signals 310. Thepilot signals 310 enable channel sensing. The pilot signals 310 may beuplink pilot signals, downlink pilot signals, and/or sidelink pilotsignals. The pilot signals 310 may be cell-specific and/orterminal-specific. The pilot signals 310 may have well-defined transmitproperties. Based on a comparison of receive properties with thetransmit properties, it is possible to conclude on the channelcondition. Each pilot signal may comprise one or more symbols, e.g.,OFDM symbols. The symbols of the pilot signals may be generated by asequence generator. Different pilot signals communicated in the sameresources 305 may be encoded orthogonally with respect to each other byCDMA techniques; this may be achieved by appropriately designing thesequence generator. A sequence of subsequently communicated pilotsignals 310 can be generated based on the sequence generator. Thesequence generator can map, e.g., a certain resource 305 at which therespective pilot signal is communicated to a real and imaginary parts ofthe respective OFDM symbol. Thus, the particular symbol values of thepilot signals 310 may vary from instance to instance according to thesequence generator.

Turning again to FIG. 1, the eNB 112 is connected with a gateway nodeimplemented by a serving Gateway (SGW) 117. The SGW 117 may route andforward payload data and may act as a mobility anchor during handoversof the terminals 130-1, 130-2 between neighboring cells.

The SGW 117 is connected with a gateway node implemented by a packetdata network Gateway (PGW) 118. The PGW 118 serves as a point of exitand point of entry of the cellular network 110 for data towards a packetdata network 121 (PDN): for this purpose, the PGW 118 is connected withthe PDN 121. There may be more than one PDN 121. Each PDN 121 isuniquely identified by an access point name (APN). The APN is used bythe terminals 130-1, 130-2 to seek access to the to a certain PDN 121,e.g., the Internet.

The PGW 118 can be an endpoint of an end-to-end connection 160 (dashedline in FIG. 1) for packetized payload data of the terminal 130-1. Theend-to-end connection 160 may be used for communicating data of aparticular service. Different services may use different end-to-endconnections 160 or may share, at least partly, a certain end-to-endconnection. The end-to-end connection 160 may be implemented by one ormore bearers which are used to communicate service-specific data. An EPSbearer which is characterized by a certain set of quality of serviceparameters indicated by the QoS class identifier (QCI).

FIG. 3 illustrates aspects with respect to allocation of resources 305for communication of pilot signals 311-318. In particular, FIG. 3illustrates aspects with respect to repetitive resource mappings 301,301A. While hereinafter reference is predominantly made to repetitiveresource mappings, in other examples also non-repetitive resourcemappings may be employed. The resource mappings 301, 301A define theoccupation of resources 305 for a certain type of pilot signal for acertain terminal 130-1, 130-2. Different resource mappings 301, 301A mayavoid interference by techniques of FDMA, TDMA, and/or CDMA.

In FIG. 3, an excerpt of the repetitive resource mappings 301, 301A fora given transmission interval 302 is illustrated; e.g., the transmissioninterval 302 may be a radio frame, a frame, a subframe, or a time slot.Repetitions of the repetitive resource mappings 301, 301A may beimplemented for subsequent time intervals.

In the example of FIG. 3, first pilot signals 311-314 and second pilotsignals 315-318 are illustrated. The first pilot signals 311-314 (fullblack in FIG. 3) are communicated according to the repetitive resourcemapping 301 between a terminal 130-1 and the eNB 112; the second pilotsignals 315-318 are communicated according to the repetitive resourcemapping 301A between a terminal 130-2 and the eNB 112. E.g., the firstpilot signals 311-314 may be UL pilot signals transmitted by theterminal 130-1 and received by the eNB 112; it is also possible that thefirst pilot signals 311-314 are DL pilot signals transmitted by the eNB112 and received by the terminal 130-1. Similar considerations apply tothe second pilot signals 315-318 with respect to the terminal 130-2.

It is possible that each type of pilot signal has an associated uniquerepetitive resource mapping 301, 301A. I.e., different repetitiveresource mappings 301, 301A may distinguish different types of pilotsignals from each other. It is also possible that different terminals130-1, 130-2 employ different repetitive resource mappings 301, 301A;this may allow the eNB 112 to distinguish between the identities of theoriginators of received UL pilot signals.

In FIG. 3, silent periods 307 of the terminal 130-1 are illustrated; theterminal 130-1 does not transmit during the silent periods 307. Byimplementing such silent periods 307 interference can be mitigated withrespect to further terminals which require protected resources forcommunication of, e.g., for the pilot signals (not illustrated in FIG.3).

As can be seen from FIG. 3, in order to avoid interference betweencommunicating the first pilot signals 311-314 and communicating thesecond pilot signals 315-318, FDMA techniques are employed with respectto the repetitive resource mappings 301, 301A.

FIG. 4 illustrates aspects with respect to allocation of resources 305for communication of pilot signals 311-318. FIG. 4 generally correspondsto FIG. 3. However, in the scenario of FIG. 4, instead of employing FDMAtechniques for communicating the first pilot signals 311-314 and thesecond pilot signals 315-318, respectively, TDMA techniques are employedwith respect to the repetitive resource mappings 301, 301A.

As can be seen from FIG. 4, the terminal 130-2 communicates the pilotsignals 315-318 during the silent periods 307 of the terminal 130-1.Because of this, the terminal 130-1 is able to receive the second pilotsignals 315-318 communicated by the terminal 130-2. Generally, it wouldalso be possible that the terminal 130-1 in the scenario of FIG. 3receives the second pilot signals 315-318 communicated by the terminal130-2; e.g., such a scenario may be facilitated by duplex communicationcapability of the terminal 130-1.

The repetitive resource mappings 301, 301A may be specified by controlsignaling. E.g., a plurality of candidate resource mappings may bepredefined. E.g., based on the control signaling, the particularresource mapping applicable to communication of the pilot signals311-314, 315-318 may be selected. E.g., the Physical Cell Identity maybe associated with a particular resource mapping, see 3GPP TS 36.211V13.1.0, 2016, Chapter 6.10.1.

The resource mappings 301, 301A of FIGS. 3 and 4 can be repeatedlyapplied. The periodicity of the repetitions may correspond to thetransmission interval 302 or multiple transmission intervals 302.

Hereinafter, with respect to the signaling diagrams of FIGS. 8A, 8B, 9A,9B, 10, 11A, 11B, 20-25 reference is made to pilot signals. These pilotsignals can be configured according to the pilot signals 310-318 asdiscussed with respect to FIGS. 3A and 3B.

FIG. 5 illustrates aspects with respect to repetitions of the repetitiveresource mapping 301. In FIG. 5, the mapping of the repetitive resourcemapping 301 to subsequent transmission intervals 302 is illustrated. Inthe example of FIG. 5, the repetitive resource mapping 301 is repeatedfor each transmission interval 302; thus, a periodicity 303 of therepetitive resource mapping 301 corresponds to the duration of thetransmission interval 302.

FIG. 6 illustrates aspects with respect to repetitions of the repetitiveresource mapping 301. In FIG. 6, the mapping of the repetitive resourcemapping 301 to subsequent transmission intervals 302 is illustrated. Inthe example of FIG. 6, the repetitive resource mapping 301 is repeatedevery second transmission interval 302; thus, the periodicity 303 of therepetitive resource mapping 301 corresponds to twice the duration of thetransmission interval 302. In other examples, even longer periodicitiesare conceivable. Different repetitive resource mappings may havedifferent periodicities.

FIG. 7 illustrates aspects with respect to a terminal 130-1 receivingthe UL pilot signals transmitted by terminals 130-2, 130-3. In FIG. 7,the terminal 130-1 is positioned in between the terminals 130-2, 130-3.The terminals 130-2, 130-3 transmit UL pilot signals. The UL pilotsignals are intended for the eNB 112. Thus, the transmit power of the ULpilot signals transmitted by the terminals 130-2, 130-3, 130-4 is setsuch that the eNB 112 defining a cell 112A can receive the UL pilotsignals. The eNB 112 may implement channel sensing according toreference techniques based on the received UL pilot signals.

The UL pilot signals are intended for the eNB 112 by communicating themaccording to a certain repetitive resource mapping and/or generating asequence of the pilot signals according to a certain sequence generator,the certain repetitive resource mapping and/or the certain sequencegenerator being pre-negotiated between the eNB and the transmittingterminals 130-2, 130-3. Because the UL pilot signals are intended forthe eNB 112, the eNB 112 is configured to determine at least oneproperty of the UL pilot signals and estimate a condition of a channel261-263 based on the determined at least one property. Thus, the eNB 112may perform channel sensing based on the received UL pilot signals.

The UL pilot signals are associated with a certain transmit power. Thetransmit power defines the coverage area 130-2A, 130-3A at which thepilot signals can be received (illustrated in FIG. 7 by the dashedline). As can be seen from FIG. 7, the terminal 130-1 can receive the ULpilot signals transmitted by the terminals 130-2, 130-3. The terminal130-1 cannot receive the UL pilot signals transmitted by a terminal130-4.

FIG. 8A illustrates aspects with respect to the terminal 130-1 receivingthe UL pilot signals 901 transmitted by the terminal 130-2. FIG. 8A is asignaling diagram illustrating the communication between the eNB 112 andthe terminal 130-1 and the terminal 130-2.

The terminal 130-2 transmits an UL pilot signal 901. The UL pilot signal901 may be intended for the eNB 112. E.g., the UL pilot signal 901 maybe cell-specific for the cell 112A and/or may be terminal specific forthe terminal 130-2. The eNB 112 receives the UL pilot signal 901. TheeNB 112 performs channel sensing based on the received UL pilot signal901.

Communication of the UL pilot signal 901 is intercepted by the terminal130-1. The terminal 130-1 receives the UL pilot signal 901 transmittedby the terminal 130-2. Then, the terminal 130-1 transmits, on the radiolink 101 to the eNB 112, and UL report message 902 indicative of aproperty of the received UL pilot signal 901. The eNB 112 receives, onthe radio link 101 and from the terminal 130-1, the UL report message902 indicative of the property of the UL pilot signal 901 received bythe terminal 130-1 and transmitted by the terminal 130-2.

The UL report message 902 may enable the eNB 112 gathering additionalinformation on the condition of the radio link 101 in the area of theterminal 130-1. Based on this, channel sensing performed by the eNB 112may be executed at a higher accuracy. Remote channel sensing may beperformed.

E.g., it is possible that the UL report message 902 is indicative of oneor more properties selected from the group comprising: an amplitude ofthe received UL pilot signal 901; a phase of the received UL pilotsignal 901; a resource 305 at which the received UL pilot signal 901 iscommunicated; a time offset of the received UL pilot signal 305, e.g.,with respect to a synchronized clock of the eNB 112 and the terminals130-1, 130-2; and an angle of arrival of the received UL pilot signal901. Such properties allow for accurate channel sensing. Remote channelsensing may be performed.

FIG. 8B illustrates aspects with respect to the terminal 130-1 receivingthe UL pilot signal 901 transmitted by the terminal 130-2. FIG. 8Bgenerally corresponds to FIG. 8A; however, in the example of FIG. 8B,the UL pilot signal 901 is only received by the terminal 130-1, but notreceived by the eNB 112. Such a scenario may be applicable where theterminal 130-1 is attached to the cellular network 100 via the eNB 112,but where the terminal 130-2 is attached to the cellular network via afurther access node (not illustrated in FIG. 8B). The further accessnode may receive the pilot signal 901 and may perform channel sensingbased on the received pilot signal 901. Thus, in the various examplesdescribed herein, it is not germane that the UL report message 902 isintended for the same access node as the at least one UL pilot signal901.

In the examples of FIGS. 8A, 8B, the UL report message 902 is indicativeof at least one property of a single UL pilot signal 901. In otherexamples, information on a plurality of UL pilot signals may beaggregated into a single UL report message. Thereby, signaling overheadis reduced and traffic on the radio link 101 is reduced.

FIG. 9A illustrates aspects with respect to the terminal 130-1 receivinga plurality of UL pilot signals 911-913 transmitted by the terminal130-2. FIG. 9A generally corresponds to the example of FIG. 8A, however,in the example of FIG. 9A information on a plurality of UL pilot signals911-913 is aggregated into the UL report message 902 to reduce signalingoverhead.

While in the example of FIG. 9A all UL pilot signals 911-913 originatefrom the same terminal 130-2, in other examples it is possible that theterminal 130-1 receives a plurality of pilot signals originating from aplurality of terminals. It is also possible to aggregate information ona plurality of pilot signals originating from a plurality of terminalsinto a single UL report message 902. In a scenario, channel sensing maythus be facilitated by including an indicator indicative of the identityof the originator of the received UL pilot signals in the UL reportmessage 902. The indicator may be explicitly or implicitly indicative ofthe identity, e.g., via the particular repetitive resource mapping 301,301A.

In various examples, it is possible that the UL report message 902includes the at least one property resolved for each one of the UL pilotsignals 911-913. In other examples, it is also possible that the ULreport message 902 includes an average or an otherwise derived valuewhich is determined based on a combination of the plurality of receivedUL pilot signals 911-913. E.g., certain properties such as the amplitudeand/or the phase of the received UL pilot signals 911-913 may beaveraged and the corresponding average may be included in the UL reportmessage 902. Thereby, signaling overhead and traffic on the radio link101 is reduced.

FIG. 9B illustrates aspects with respect to the terminal 130-1 receivinga plurality of UL pilot signals 911-913 transmitted by the terminal130-2. FIG. 9B generally corresponds to the example of FIG. 9A, however,in the example of FIG. 9B the terminal 130-1 does not receive the ULpilot signal 911.

A first reason for the terminal 130-1 not receiving the UL pilot signal911 may be that the UL pilot signal 911 is transmitted at a lowertransmit power by the terminal 130-2 if compared to the UL pilot signals912, 913. E.g., the terminal 130-2 may be configured to temporarilyboost the transmit power of the UL pilot signals 912, 913 in order tofacilitate reception thereof by the terminal 130-1. Thus, the terminal130-1 may be out-of-range with respect to the UL pilot signal 911transmitted at the lower transmit power; while the terminal 130-1 may bewithin the range 130-2A with respect to the UL pilot signals 912, 913.

The second reason for the terminal 130-1 not receiving the UL pilotsignal 911 may be that the terminal 130-1, in between communication ofthe UL pilot signals 911, 912, has moved into range 130-2A of UL pilotsignal transmission by the terminal 130-2.

In a scenario according to FIG. 9B, channel sensing may thus befacilitated by including resource identification information of thereceived UL pilot signals 912, 913 in the UL report message 902.Resource identification information may include resource locationinformation and/or timestamp information.

FIG. 10A illustrates aspects with respect to the terminal 130-1receiving a plurality of UL pilot signals 921, 923 transmitted by theterminal 130-2. FIG. 10A generally corresponds to the example of FIG.9A; however, in the example of FIG. 10A, the terminal 130-1 does notreceive the pilot signal 922. This is because the UL pilot signal 922 isnot communicated during a silent period 307. In the example of FIG. 10A,the terminal 130-1 is only able to receive pilot signals during a silentperiod 307. This may be because the terminal 130-1 is restricted inhardware operation.

Thus, generally, according to the various examples described herein itis not mandatory that the terminal 130-1 receives all of a sequence ofthe UL pilot signals transmitted by the terminal 130-2 in the sequenceof transmission intervals 302; rather, it is sufficient if the terminal130-1 receives the UL pilot signals in a subset of the sequence oftransmission intervals 302. E.g., it is possible that the transmissionintervals 302 of the subset—at which the terminal 130-1 receives ULpilot signals—are scheduled between the terminal 130-1 and the eNB 112.

FIG. 10B illustrates aspects with respect to the terminal 130-1receiving the UL pilot signals 927, 928 transmitted by the terminals130-2, 130-3. FIG. 10B generally corresponds to FIGS. 8A and 8B;however, the terminal 130-1 receives and aggregates information on ULpilot signals 927, 928 transmitted by two terminals 130-2, 130-3. The ULpilot signals 927, 928 may or may not be intended for one and the sameeNB 112 and may or may not be received by the eNB 112. The reportmessage 929 is indicative of a properties of both pilot signals 927,928.

FIG. 11A illustrates aspects with respect to the terminal 130-1receiving an UL pilot signal. FIG. 11A further illustrates aspects ofsporadically scheduling the transmission intervals 302 of the subsetbetween the eNB 112 and the terminal 130-1. A scheduling control message931 is transmitted by the eNB 112 and received by the terminal 130-1.The scheduling control message 931 is indicative of resourceidentification information/timing of the UL pilot signal 932subsequently transmitted by the terminal 130-2. The scheduling controlmessage 931 prompts the terminal 130-1 to receive the UL pilot signal932. In response to receiving the scheduling control message 931, theterminal 130-1 receives the UL pilot signal 932.

By employing such sporadic scheduling, the terminal 130-1 is releasedfrom the need of activating receiver circuitry blindly, i.e., withoutknowledge of the timing of UL pilot signals transmitted by the terminal130-2. Energy consumption can be reduced.

FIG. 11B illustrates aspects with respect to the terminal 130-1receiving a plurality of UL pilot signals 942, 944. FIG. 11B furtherillustrates aspects of persistently scheduling the transmissionintervals 302 of the subset between the eNB 112 and the terminal 130-1.In the example of FIG. 11B, the scheduling control message 931 specifiesreoccurring points in time at which the terminal 130-1 persistentlyreceives UL pilot signals 942, 944 transmitted by the terminal 130-2.E.g., such reoccurring points in time may be defined with respect tocertain periodicity 931A.

As can be seen from FIG. 11B, the UL pilot signals 942, 944 are part oftransmission intervals 302 of a corresponding subset; on the other hand,the UL pilot signal 943 is not received by the terminal 130-1, becausethe corresponding transmission interval 302 is not part of the subset.The report message 902 includes the property of the received UL pilotsignals 942, 944.

Such scenarios according to the examples of FIGS. 11A, 11B of schedulingthe transmission intervals 302 of the subset between the terminal 130-1and the eNB 112 may be in particularly useful where the terminal 130-2,from time to time, temporarily increases the transmit power of the ULpilot signals. Then, it can be ensured that the terminal 130-1 activatesthe receiver circuitry of the interface to be able to receivepower-boosted UL pilot signals. Similar considerations apply if the eNB112, from time to time, transmits power-boosted DL pilot signals.

FIG. 12 illustrates aspects with respect to increasing the transmitpower of the UL pilot signals. FIG. 12 generally corresponds to FIG. 7.However, from a comparison of FIGS. 7 and 12, it is apparent that therange 130-4A of the UL pilot signals transmitted by the terminal 130-4is increased for the scenario of FIG. 12. This is because the terminal130-4 transmits UL pilot signals at a higher transmit power for thescenario of FIG. 12. In order to avoid increased interference due topower-boosted transmission of UL pilot signals, a time-limited,temporary increase of the transmit power is possible.

Such a temporary boosting of the transmit power is conceivable not onlyfor UL pilot signals in scenarios described above, but generally for alltypes of UL pilot signals including UL pilot signals, DL pilot signals,sidelink pilot signals, cell-specific pilot signals, andterminal-specific pilot signals. Then, additional nodes or devices mayreceive the power-boosted pilot signals; the power-boosted pilot signalsmay have beacon functionality.

FIG. 13A illustrates aspects with respect to transmitting pilot signals311-314 in a first subset 321 of transmission intervals 302 at thenon-zero first transmit power; and transmitting UL pilot signals 311-314in the second subset 322 of the transmission intervals 302 at a non-zerosecond transmit power which is larger than the first transmit power. Byemploying, both, the first and second transmit power, the tradeoffbetween interference (due to the larger second transmit power) andinaccuracies of channel sensing (due to fewer nodes receiving the pilotsignals having the lower first transmit power) can be optimized.Increased coverage is traded against the added interference.

In the example of FIG. 13A, thus, the transmit power of pilot signals311-314 of the same type is temporarily adjusted. A temporary transmitpower boost is implemented for the pilot signals 311-314 of a giventype. The pilot signals 311-314 are all of the same type, because thesame repetitive resource mapping 301 is used. The various pilot signals311-314 transmitted at the first transmit power the second transmitpower also belong to the same sequence which is associated with a singlesequence sequence generator, sometimes also referred to as generatorcode. E.g., examples of sequence generators are given by 3GPP TS 36.211V13.0.0 (2015-12); e.g., for the CRS, the sequence generation isspecified by chapter 6.10.1.1; e.g., for the SRS, the sequencegeneration is specified in chapter 5.5.3.1.

From FIG. 13A it is apparent that the transmission intervals 302 of thesecond subset 322 are arranged in-between the transmission intervals 302of the first subset 321. In the example of FIG. 13A, the first subset331 and the second subset 322 are interleaved in time domain. Hence, thefirst subset 331 and the second subset 332 are alternatingly activewithin an arbitrary time period. Such an interleaving in time domain maybe applicable to the various examples discussed herein.

Generally, the first subset 331 and the second subset 332 could be atleast partly different from each other, e.g., with respect to at leastone of the following: time domain, frequency domain, code domain, and/orspatial domain. Alternatively or additionally, different duplexingtechniques and/or interleaving techniques can be combined with respectto each other. In general, the first subset 331 and the second subset332 may be in some manner distinguishable from each other. E.g., thefirst and second subsets 331, 332 may be distinguishable from each otherusing either time, frequency or spatial means, or combinations thereof.Code division is also a possibility.

From FIG. 13A it is apparent that transmission intervals 302 of thesecond subset 322 are reoccurring, e.g., at a periodicity 322A. To avoidexcessive interference due to a large number of power-boosted pilotsignals 311-314, it can be desirable to limit the number of transmissionintervals 302 of the second subset 302. E.g., the size—i.e., the numberof transmission intervals 302 included in—the first subset 321 may belarger than the size of the second subset 322 at least by a factor of 2,preferably by at least a factor of 100, more preferably by at least afactor of 1000 (in the example of FIG. 13A, the size of the first subset321 is larger than the size of the second subset 322 by a factor of 3).

It is not germane that all pilot signals 311-314 within a transmissioninterval 302 of the second subset 321 are transmitted at the secondtransmit power. Generally, it is sufficient if a single one or afraction of all pilot signals 311-314 within a given transmissioninterval 302 of the second subset 321 are transmitted at the secondtransmit power, while the remaining pilot signals 311-314 aretransmitted at the first transmit power. In some examples, it is,however, possible, that all pilot signals 311-314 within a transmissioninterval 302 of the second subset 321 are transmitted at the secondtransmit power.

FIG. 13B illustrates aspects with respect to the first transmit power231 and the second transmit power 232 associated with the first subset321 and the second subset 322, respectively. From FIG. 13B it isapparent that the second transmit power 232 is larger than the firsttransmit power 231 by a factor 233. E.g., this factor may amount to atleast 1 dB, preferably to at least 3 dB, more preferably to at least 10dB. E.g., the second transmit power 232 may be determined to equal amaximum transmit power supported by a respective interface or analoguetransmitter stage of the transmitting device. Beyond this, further orother considerations may be taken into account when determining thefactor 233; examples include: and at least partly random process and/oran optimization process. E.g., optimization may occur with respect toelements selected from the group comprising: interference; an accuracyof channel sensing; the tradeoff between interference and coverage; etc.Beyond such examples, further or other considerations can be taken intoaccount when determining the factor 233. Examples include: a position ofthe terminal communicating the pilot signals; and a handover of theterminal communicating the pilot signals.

FIG. 14 illustrates aspects with respect to determining the factor 233between the second transmit power 232 and the first transmit power 231.In the example of FIG. 14, the factor 233 is constant over time at afinite, i.e., non-zero, value.

FIG. 15 illustrates aspects with respect to determining the factor 233between the second transmit power 232 and the first transmit power 231.In the example of FIG. 15, the factor 233 varies over the course oftime. This may be, e.g., due to random contributions to the determiningof the factor 233; a mobility/time-varying position of the terminalcommunicating the pilot signals; and a handover of the terminaloccurring at a certain point in time. Thus, the time-dependency of thefactor 233 may be context-dependent.

FIG. 16 illustrates aspects with respect to determining the factor 233between the second transmit power 232 and the first transmit power 231.In the example of FIG. 16, the factor 233 varies over the course oftime. In particular, the factor 233 varies between zero dB and a finitevalue. As can be seen, in various examples power boosting of pilotsignals may be selectively executed depending on certain triggercriteria and/or context-dependent. I.e., communicating the pilot signalshaving the second transmit power may be selectively executed dependingon certain trigger criteria and/or context-dependent.

While above various aspects have been explained above with respect tothe time-dependency and the determining of the factor 233 between thesecond transmit power 232 and the first transmit power 231, similarconsiderations may be readily applied to the time-dependency and thedetermining of a factor between the size of the second subset 232 andthe size of the first subset 231.

FIG. 17 illustrates aspects with respect to handover scenario. FIG. 17illustrates aspects with respect to a scenario of a terminal 130-1transmitting UL pilot signals. The terminal 130-1 is attached to thecellular network via the eNB 112-1. In FIG. 17, the terminal 130-1 islocated close to the edge of the cell 112-1A of the eNB 112-1. A firstrange 130-1A associated with the first transmit power 231 is illustrated(dotted line in FIG. 17); furthermore, a second range 130-1B associatedwith a second transmit power 232 is illustrated (dashed line in FIG.17). It is apparent that only the pilot signals having the secondtransmit power 232 can be received by, both, the enB 112-1, as well asthe eNB 112-2 associated with the cell 112-2A (the eNB 112-3 cannotreceive any UL pilot signals transmitted by the terminal 130-1). Channelsensing by the eNB 112-2 can thus be facilitated by using the pilotsignals having the second transmit power 232. Further, by employing thesecond transmit power 232 for the UL pilot signals in the transmissionintervals 302 of the second subset 322, the eNB 112-2 can bepreemptively notified of the terminal 130-1 approaching the cell 112-2A.This information can be used to reliably perform the handover from theeNB 112-1 to the eNB 112-2.

In some examples, power boosting, i.e., transmitting the pilot signalshaving the second transmit power 232, may be selectively executed if theterminal 130-1 approaches the edge of the cell 112-1A; i.e., it ispossible to consider the position of the terminal 130-1 when determiningthe factor 233 between the second transmit power 232 and the firsttransmit power 231 (cf. FIG. 16).

In some examples, it can be desirable to schedule, between the eNB 112-1and the eNB 112-2, the transmission intervals 302 of the second subset322. This can be done in order to mitigate inter-cell interferencecaused by the comparably high second transmit power 232. Such schedulingmay include control signaling implemented via the core network betweenthe eNB's 112-1, 112-2. Such scheduling may include implementing acommon time reference for the eNB's 112-1, 112-2; thus, timesynchronization between the eNB's 112-1, 112-2 can be implemented.

In a first example, such scheduling may relate to co-scheduling pilotsignals communicated by the eNB 112-1—such as the UL pilot signalstransmitted by the terminal 130-1 and received by the eNB 112-1—withsignals communicated by the eNB 112-2; i.e., the pilot signalscommunicated by the eNB 112-1 may be scheduled in resources sharedbetween the eNB 112-1 and the eNB 112-2. In a second example, suchscheduling may relate to orthogonally scheduling pilot signalscommunicated by the eNB 112-1—such as the UL pilot signals transmittedby the terminal 130-1 and received by the eNB 112-1—with signalscommunicated by the eNB 112-2; i.e., the pilot signals communicated bythe eNB 112-1 may be scheduled in resources 305 dedicated to the eNB112-1 and not shared with the eNB 112-2. Orthogonality may be achievedby at least one of the following: FDMA, TDMA, and CDMA. E.g., it ispossible to selectively use orthogonal resources 305 depending on aposition of the terminal 130-1. E.g., the transmission intervals 302 ofthe second subset 322 can be selectively scheduled in resources 305shared between the eNB 112-1 and the eNB 112-2 depending on the positionof the terminal 130-1 communicating the pilot signals. In one example,orthogonally scheduling can be preferred where the terminal 130-1 islocated close to the cell edge bordering to the eNB 112-2 (dashed areain FIG. 17). In such an example, strong inter-cell interference isavoided, because orthogonal resources are employed close to the edge ofthe cell 112-1A; on the other hand, spectral efficiency is achieved byusing shared resources if the terminal 130-1 is positioned away from theedge of the cell 112-1A (i.e., outside the dashed area in FIG. 17).

FIG. 18 illustrates aspects with respect to a further handover scenario.In the example of FIG. 18, a micro cell 112-2A is implemented by the eNB112-2. Sometimes, the micro cell is referred to as pico cell. A macrocell 112-1A is implemented by the eNB 112-1. The terminal 130-1 isattached to the cellular network 100 via the eNB 112-2. Because theterminal 130-1 communicates with the eNB 112-2 implementing the microcell 112-2A, the first transmit power 231 is dimensioned comparablysmall as can be seen from the small range 130-1A. This is done in orderto avoid interference with pilot signals communicated by the eNB 112-1.The second transmit power 232 is dimensioned significantly larger as canbe seen from the range 130-1B. In particular, the larger second transmitpower 232 facilitates reception of UL pilot signals transmitted by theterminal 130-1 by the eNB 112-1. Based on the received UL pilot signals,the eNB 112-1 can conclude on the channel condition between the terminal130-1 and the eNB 112-2. In particular, backhaul signaling between theeNB's 112-1, 112-2 can be reduced. Such a reduction of backhaulsignaling may be in particularly relevant where unlicensed frequencybands are used for the communication between the terminal 130-1 and theeNB 112-2.

FIG. 19 illustrates aspects with respect to a further handover scenario.In the example of FIG. 19, micro cells 112-2A, 112-3A are implemented bythe eNB's 112-2, 112-3, respectively. A macro cell 112-1A is implementedby the eNB 112-1. The terminal 130-1 is attached to the cellular network100 via the eNB 112-1. When the terminal 130-1 approaches one of themicro cells 112-2A, 112-3A, such an approach can be preemptivelydetected by the respective eNB 112-2, 112-3 directly by means of thepilot signals transmitted at the higher second transmit power 232, seethe corresponding range 130-1B. In particular, because the pilot signalstransmitted at the second transmit power 232 can be received by botheNB's 112-2, 112-3, it is possible to select the most appropriate microcell 112-2A, 112-3A. Backhaul signaling between the eNB 112-1 and theeNB 112-2, 112-3 is reduced or avoided.

FIG. 20 illustrates aspects with respect to communicating pilot signalshaving the first transmit power 231 in the first subset 321 andcommunicating the pilot signals having the second transmit power 232 inthe second subset 322. FIG. 20 is a signaling diagram of signalingbetween the eNB 112 and the terminal 130-1. In the example of FIG. 20,the decision logic on implementing communication of the pilot signalshaving the second transmit power 232 resides at the eNB 112. In detail,at 1001, the eNB 112 decides to implement communication of the pilotsignals having the second transmit power 232.

FIG. 20 further illustrates aspects with respect to scheduling thetransmission intervals 302 of the second subset 322 between the eNB 112and the terminal 130-1. At 1001, a timing 322A of the transmissionintervals 302 of the second subset 322 is determined. In the example ofFIG. 20, the timing 322A corresponds to reoccurring, e.g., at a givenperiodicity, transmission intervals 302 of the second subset 322.Non-periodically reoccurring transmission intervals 302 are possible.

Next, a control message 1002 indicative of the second transmit power232, and optionally indicative of the first transmit power 231, iscommunicated from the eNB 112 to the terminal 130-1. E.g., the controlmessage 1002 can be a RRC control message. The control message 1002 isalso indicative of the timing 322A. Based on the control message 1002,the transmission intervals 302 of the second subset 322 are persistentlyscheduled, e.g., scheduled until a new control message 1002 iscommunicated from the eNB 112 to the terminal 130-1

Then, the terminal 130-1 transmits UL pilot signals 1003-1007. Thesecond subset 322 is interleaved into the first subset 321; in detail,the pilot signals 1004 having the second transmit power 232 istransmitted in-between the pilot signals 1003, 1005 having the firsttransmit power 231. However, such time-domain interleaving is an optiononly. In other examples, other ways of distinguishing the first andsecond subsets 321, 322 may be chosen; e.g., the first and secondsubsets 321, 322 may be distinguished from each other with respect to atleast one of the following: in frequency domain, spatial domain, codedomain, etc.

FIG. 21 illustrates aspects with respect to communicating pilot signalshaving the first transmit power 231 in the first subset 321 andcommunicating the pilot signals having the second transmit power 232 andthe second subset 322. The example of FIG. 21 generally corresponds tothe example of FIG. 20. In the example of FIG. 21, the transmissionintervals 302 of the second subset 322 are sporadically scheduled. Inparticular, at 1001, the timing 322A is determined. Also in the exampleof FIG. 20, the timing 322A corresponds to reoccurring, e.g., at a givenperiodicity, transmission intervals 302 of the second subset 322.However, in the scenario of FIG. 21, dedicated control messages 1014,1017 are communicated from the eNB 112 to the terminal 130-1, each oneof the dedicated control messages 1014, 1017 triggering transmission ofa single UL pilot signal 1015, 1018. Hence, the transmission intervals302 of the second subset 322 are sporadically scheduled. It is notrequired that the terminal 130-1 is informed on the timing 322A, becauseeach control message 1014, 1017 individually triggers transmission of arespective UL pilot signal 1015, 1018 having the second transmit power232.

In the scenarios of FIGS. 20 and 21, the decision logic for deciding onusing the higher, second transmit power 232 resides at the eNB 112.Likewise, the second transmit power 232 is determined at the eNB 112.The eNB 112 is also informed on the timing 322A with which thetransmission intervals 302 of the second subset 322 are scheduled. Thus,the eNB 112 can perform accurate channel sensing based on thewell-defined parameters of the UL pilot signals transmitted in thesecond subset 322 at the second transmit power 232.

In some scenarios, it is also possible that the decision logic fordeciding on using the higher, second transmit power 232 at least partlyresides at the terminal 130-1. Here, the terminal 130-1 may decide onthe timing 322A of the transmission intervals 302 of the second subset322 and/or on the second transmit power 232. Such scenarios may beapplicable where control signaling is limited, e.g., due to the usage ofunlicensed bands and/or different involved operators. Here, bottom-upscheduling, autonomously executed by individual terminals or other nodesmay be of relevance.

FIG. 22 illustrates aspects with respect to communicating pilot signals1021, 1024-1026 having the first transmit power 231 in the first subset321 and communicating the pilot signals 1023 having the second transmitpower 232 in the second subset 322. In the example of FIG. 22, thedecision logic for deciding on using the higher second transmit power232 resides at the terminal 130-1.

In the example of FIG. 22, the terminal 130-1 transmits UL pilot signals1021, 1024-1026 in the first subset 321 and at the first transmit power;the terminal 130-1 transmits the UL pilot signals 1023 at the higher,second transmit power 232. The UL pilot signal 1023 is indicative of thesecond transmit power 232 such that the eNB 112 is informed accordingly.The second transmit power 232 is determined at the terminal 130-1. Inorder to enable accurate channel sensing at the eNB 112, the eNB 112should be informed on the second transmit power 232.

Different scenarios are conceivable for implementing the pilot signal1023 to be indicative of the second transmit power 232. E.g., the pilotsignal 1023 can be explicitly or implicitly indicative of the secondtransmit power 232. E.g., the sequence of pilot signals 1021, 1023-1026may be associated with the same sequence generator. Thus, the samesequence generator may be used for generation of the pilot signals 1021,1023-1026. In an example, the respective transmit power of each pilotsignals 1021, 1023-1026 is an input of the generator code. Inparticular, there may be a unique mapping between the symbols output bythe sequence generator for a given pilot signal 1021, 1023-1026 and thetransmit power input to the sequence generator. Thus, based on theparticular symbol of a given pilot signal 1021, 1023-1026, it canpossible to conclude on the respective transmit power 231, 232; as such,the pilot signal 1023 is implicitly indicative of the second transmitpower 232. This reduces the control signaling overhead.

In a further scenario, an explicit flag may be appended to the pilotsignal 1023; this flag may be indicative of the second transmit power232, e.g., according to predefined rules, etc. As such, the pilot signal1023 is explicitly indicative of the second transmit power 232.

By such techniques it is possible that further terminals receiving thepower-boosted pilot signal 1023 (cf. FIGS. 7, 8A, 8B, 9A, 9B, 10, 11)are also aware of the second transmit power 232. A respective UL reportmessage 902 could include an indicator indicative of the second transmitpower 232.

FIG. 23 illustrates aspects with respect to communicating pilot signals10131 1035-1037 having the first transmit power 231 in the first subset321 and communicating the pilot signals 1033 having the second transmitpower 232 in the second subset 322. The example of FIG. 23 generallycorresponds to the example of FIG. 22. 1031 corresponds to 1021. 1032corresponds to 1022. 1033 corresponds to 1023. 1035 corresponds to 1024.1036 corresponds to 1025. 1037 corresponds to 1026.

The decision logic for deciding on using the higher second transmitpower 232 resides at the terminal 130-1. In the example of FIG. 23,instead of implementing the pilot signal 1033 having the second transmitpower 232 to be indicative of the second transmit power 232, a dedicatedcontrol message 1034 is communicated from the terminal 130-1 to the eNB112. E.g., the control message 1034 may be a RRC control message or thelike. The control message 1034 may be communicated in a temporal contextwith the pilot signal 1033, e.g., at the same transmission interval 302or the like. The control message 1034 may include an indicatorindicative of the UL pilot signal 1033.

If the control message 1034 is broadcasted to other devices, it ispossible that further terminals receiving the power-boosted pilot signal1023 (cf. FIGS. 7, 8A, 8B, 9A, 9B, 10, 11) are also aware of the secondtransmit power 232. A respective UL report message 902 could include anindicator indicative of the second transmit power 232.

FIG. 24 illustrates aspects with respect to handover scenario. FIG. 24is a signaling diagram of communication between the eNB 112-1, the eNB112-2, and the terminal 130-1. Aspects discussed with respect to FIG. 24may be employed, e.g., in the scenario of FIGS. 17-19.

In a handover process, it is easier for the eNB 112-2 to be aware of theterminal 130-1 approaching the coverage area if the terminal 130-1employs power-boosted pilot signals. E.g., in a scenario where the eNB112-2 only receives power-boosted pilot signals, handover may beavoided, because the coverage area has not been reached. It is alsopossible to prepare for handover if based on the power-boosted pilotsignals it is judged that the terminal 130-1 approaches the coveragearea.

In the example of FIG. 24, the terminal 130-1 transmits an UL pilotsignal 1041 at the first transmit power 231. The pilot signal 1041 isreceived by the eNB 112-1 to which the terminal 130-1 is connected andvia which the terminal 130-1 is attached to the cellular network 100.The pilot signal 1041 is not received by the eNB 112-2. This is due tothe limited first transmit power 231.

The terminal 130-1 then transmits the pilot signal 1042 at the secondtransmit power 232. Both, the eNB 112-1, as well as the eNB 112-2receive the pilot signal 1042. This is due to the increased secondtransmit power 232.

Based on the received pilot signal 1042, the handover can be initiated.In a specific example of FIG. 24, the handover is initiated by thetarget eNB 112-2 by communicating a handover request 1042 from thetarget eNB 112-2 to the source eNB 112-1. In other examples, thehandover can also be initiated by the source eNB 112-1. The furtherhandover procedure can be implemented according to 3GPP TS 23.401 and3GPP TS 36.300.

FIG. 25 illustrates aspects with respect to a scheduling, between theeNBs 112-1, 112-2, the transmission intervals 302 of the second subset322. FIG. 25 is a signaling diagram of communication between the eNB112-1, the eNB 112-2, and the terminal 130-1. Aspects discussed withrespect to FIG. 25 may be employed, e.g., in the scenario of FIGS.17-19.

At least one control message 1051 is communicated between the eNB's112-1, 112-2. The at least one control message can be indicative of thetiming 322A of the transmission intervals 302 of the second subset 322.The timing 322A can be such that inter-cell interference between thecell 112-1A associated with the eNB 112-1 and the cell 112-2A associatedwith the eNB 112-2 is mitigated.

Next, a control message is communicated from the eNB 112-1 to theterminal 130-1. The control message 1052 is indicative of the timing322A. Optionally, the control message is indicative of the secondtransmit power 232 and/or the first transmit power 231. The terminal130-1 can then transmit the UL pilot signals 1053, 1054 according to thetiming 322A and optionally according to the specified first and secondtransmit power 231, 232.

FIG. 26 illustrates schematically a terminal 130 which may be employedin the various examples described herein. The terminal 130 comprises aprocessor 1301, a memory 1302, e.g., a non-volatile memory, and aninterface 1303. The interface 1303 is configured to communicate on theradio link 101. E.g., the interface 1303 may comprise an antenna arrayin order to employ MIMO or MAMI techniques. The processor 1301 isconfigured to retrieve control data from the memory 1302. Executing thecontrol data causes the processor 1302 to perform techniques asdescribed herein, e.g., relating to: receiving UL pilot signalstransmitted by a further terminal; scheduling transmission intervals ofa subset in which UL pilot signals are received; determining a propertyof the received UL pilot signal; transmitting an UL report messageindicative of the property of the received UL pilot signal;communicating pilot signals having time-varying transmit power;communicating pilot signals which are indicative of the transmit power;communicating a control message indicative of the transmit power of apilot signals; scheduling transmission intervals during which pilotsignals of a certain transmit power are communicated; and/or determininga resource mapping and/or a transmit power of pilot signals; etc.

FIG. 27 illustrates schematically and eNB 112 which may be employed inthe various examples described herein. The eNB 112 comprises a processor1121, a memory 1122, e.g., a non-volatile memory, and an interface 1123.The interface 1123 is configured to communicate on the radio link 101.E.g., the interface 1123 may comprise an antenna array in order toemploy MIMO or MAMI techniques. The processor 1121 is configured toretrieve control data from the memory 1122. Executing the control datacauses the processor 1121 to perform techniques as described herein,e.g., relating to: receiving UL pilot signals; scheduling transmissionintervals of a subset in which UL pilot signals are to be received by aterminal; determining a property of the received UL pilot signal;determining a property of the received UL pilot signals; transmitting anUL report message indicative of the property of the received UL pilotsignals; communicating pilot signals having time-varying transmit power;communicating pilot signals which are indicative of the transmit power;communicating a control message indicative of the transmit power ofpilot signal; scheduling transmission intervals during which pilotsignals of a certain transmit power are communicated; performing linkadaptation; performing channel sensing; and/or determining a resourcemapping and/or a transmit power of pilot signals; etc.

FIG. 28 is a flowchart of a method according to various embodiments.E.g., the method according to FIG. 28 may be executed by the terminalaccording to FIG. 26.

At 2001, a first terminal 130, 130-1-130-4 receives at least one ULpilot signal 310-318 transmitted by a different, second terminal 130,130-1-130-4. E.g., 2001 may be executed during silent periods 307 atwhich the first terminal 130, 130-1-130-4 does not transmit pilotsignals 310-318. E.g., 2001 may be continuously or intermittedelyexecuted by the first terminal 130, 130-1-130-4. E.g., 2001 may betriggered by a certain event. E.g., 2001 may be triggered by arespective transmission interval 302 which has been identified byscheduling; said scheduling may be between an eNB 112, 112-1-112-3 andthe first terminal 130, 130-1-130-4.

E.g., the UL pilot signal 310-310 received at 2001 may be selected fromthe group comprising: demodulation reference signal (DRS) according to3GPP TS 36.211 V13.0.0 (2015-12) chapter 5.5.2; and sounding referencesignal (SRS) according to 3GPP TS 36.211 V13.0.0 (2015-12) chapter5.5.3.

At 2002, the first terminal 130, 130-1-130-4 transmits an UL reportmessage 902. The UL report message 902 is indicative of a property ofthe received at least one UL pilot signal 310-318.

The property may be indicative of information directly relevant forchannel sensing including, e.g.: a phase of the received UL pilot signal310-318; an amplitude of the received UL pilot signal 310-318; a timeoffset of the received UL pilot signal 310-318; etc. Alternatively oradditionally, the property may be indicative of information whichenables the eNB 112, 112-1-112-3 receiving the UL report message 902 toconclude on the originator of the UL pilot signal 310-318, i.e., on theidentity of the second terminal 130, 130-1-130-4. Such a property may beselected from the group comprising: an identity of the second terminal130, 130-1-130-4; a resource 305 of the at least one UL pilot signal310-318; and resource identification information of the received atleast one UL pilot signal 310-318. E.g., based on the resource 305 ofthe at least one UL pilot signal 310-318 and/or based on the resourceidentification information, together with the knowledge of therepetitive resource mapping according to which the UL pilot signals310-318 are transmitted by the terminals connected to an access node, itis possible to conclude on the identity of the second terminal.

If at 2001 a plurality of UL pilot signals 310-318 is received,information regarding the plurality of UL pilot signals 310-318 may beaggregated into the UL report message 902 transmitted at 2002.

FIG. 29 is a flowchart of a method according to various embodiments.E.g., the method according to FIG. 29 may be executed by the eNB 112according to FIG. 27. At 2011, the eNB 112, 112-1-112-3 receives the ULreport message 902 from the first terminal 130, 130-1-130-4. The ULreport message 902 is indicative of a property of at least one UL pilotsignal 310-318 which has been received by the first terminal 130,130-1-130-4. The UL pilot signal 310-318 has been transmitted by asecond terminal 130, 130-1-130-2. It is possible that the eNB 112 alsoreceives the at least one UL pilot signal 310-318 on which the UL reportmessage 902 reports.

FIG. 30 is a flowchart of a method according to various embodiments.E.g., the method according to FIG. 30 may be executed by the terminal130 according to FIG. 26 and/or by the eNB 112 according to FIG. 27. At2021, pilot signals 310-318 having a first transmit power 231 aretransmitted and/or received (communicated). The pilot signals having afirst transmit power 231 are included in the first subset 321 oftransmission intervals 302.

At 2022, pilot signals 310-318 having a second transmit power 232 aretransmitted and/or receiving (communicated). The pilot signals havingthe second transmit power 232 are included in the second subset 322 ofthe transmission intervals 303. The first subset 321 and the secondsubset 322 are interleaved in time domain. However, such time-domaininterleaving is an option only. In other examples, other ways ofdistinguishing the first and second subsets 321, 322 may be chosen;e.g., the first and second subsets 321, 322 may be distinguished fromeach other with respect to at least one of the following: in frequencydomain, spatial domain, code domain, etc.

In the example of FIG. 30, various types of pilot signals 310-318 can beemployed for 2021 and 2022. In particular, the sign type of pilot signalcan be employed for 2021 and 2022. A type of pilot signal can becharacterized by the particular resource mapping 301 and/or the sequencegenerator for generating the respective sequences of pilot signals310-318. If the respective techniques are employed for the 3GPP LTEarchitecture, examples of types of pilot signals include, but are notlimited to: cell-specific reference signal (CRS) according to 3GPP TS36.211 V13.0.0 (2015-12) chapter 6.10.1; DL DRS according to 3GPP TS36.211 V13.0.0 (2015-12) chapter 6.10.3A; CSI reference signal accordingto 3GPP TS 36.211 V13.0.0 (2015-12) chapter 6.10.5; UL DRS according to3GPP TS 36.211 V13.0.0 (2015-12) chapter 5.5.2; and SRS according to3GPP TS 36.211 V13.0.0 (2015-12) chapter 5.5.3.

FIG. 31 is a flowchart of a method according to various embodiments.E.g., the method according to FIG. 31 can be employed in conjunctionwith the method according to FIG. 30.

At 2041, the factor between the size of the first subset 321 and thesize of the second subset 322 is determined. In some scenarios, it canbe desirable to transmit a larger number of pilot signals 310-318 at thesmaller, first transmit power 231 if compared to the number of pilotsignals transmitted at the larger, second transmit power 232; here, thefactor may amount to, e.g., 2, 10, 100, or 1000. Larger factorstypically correspond to smaller interference.

At 2042, the factor by which the second transmit power 232 is largerthan the first transmit power 231 is determined. In some scenarios, itcan be desirable to implement a comparably large factor, e.g., amountingto 1 dB, 2 dB, 3 dB, or even more. Thereby, the pilot signals having thesecond transmit power 232 can be received even in presence ofsignificant path loss, e.g., at remote positions; the correspondingrange is increased. At the same time, increased interference may result.

At 2041 and 2042, various decision criteria may be taken into accountwhen determining the respective factors. Example decision criteriainclude, but are not limited to: mobility; an at least partly randomprocess; an optimization process; a position of the terminaltransmitting and/or receiving (communicating) the pilot signal; ahandover of the terminal; etc.

E.g., if the position of the terminal is associated with increasedinter-cell interference—as may be the case if the terminal is positionedclose to the edge of a cell—, a larger factor between the size of thefirst subset 321 and the size of the second subset 322 may be determinedat 2041 and/or a smaller factor between the second transmit power 232and the first transmit power 231 may be determined at 2042. Thereby,interference is mitigated.

E.g., if a handover of the terminal is imminent, a factor between thesize of the first subset 321 and the size of the second subset 322closer to 1 may be determined. Thereby, accurate channel sensing isfacilitated. The handover can be accurately triggered.

At 2042, a control message is communicated between the respective eNB112, 112-1-112-3 and the respective terminal 130, 130-1-130-4, thecontrol message being indicative of the factors determined at 2041,2042. E.g., the control message may be implicitly indicative of thefactor between the size of the first subset 321 and the size of thesecond subset 322 determined at 2041 by scheduling a timing 322A oftransmission intervals 302 of the second subset 322.

Summarizing, above, techniques have been described which enable toefficiently communicate pilot signals such as UL pilot signals or DLpilot signals or sidelink pilot signals.

In particular, techniques have been described which enable a firstterminal receiving UL pilot signals transmitted by at least one secondterminal. Thereby, additional information on the condition of the radiolink may be collected.

Furthermore, techniques have been described which enable to temporarilyboost the transmit power of pilot signals of a given type. In detail,techniques have been described which enable to communicate pilot signalsaccording to a given repetitive resource mapping (i) in a first subsetof the sequence of transmission intervals at a first transmit power and(ii) in a second subset of the sequence of transmission intervals at ahigher, second transmit power. A sequences of these pilot signals acrossthe first and second subsets may be associated with the same sequencegenerator. By temporarily boosting the transmit power, reception of thepower-boosted pilot signals may be possible for additional entities;thereby, additional information on the condition of the radio link maybe collected.

Such techniques may be employed for various use-cases. FIG. 32 is aflowchart of a method according to various embodiments. FIG. 32illustrates aspects with respect to various use-cases relying on suchadditional information on the condition of the radio link.

At 2051, one or more properties of a received at least one pilot signal310-318 are determined. Such properties may include, but are not limitedto: an amplitude of the received at least one pilot signal 310-318; aphase of the received at least one pilot signal 310-318; a resource 305of the received at least one pilot signal 310-318; a time offset of thereceived at least one pilot signal 310-318; and an angle of arrival ofthe received at least one pilot signal 310-318.

These one or more properties can be used according to one or moreuse-cases according to 2052-2057. The respective use-cases according to2052-2057 may be employed in isolation or combined with each other.

A first use-case corresponds to 2052. At 2052, the position of a firstterminal 130, 130-1-130-4 receiving UL pilot signals 310-318 transmittedby a second terminal 130, 130-1-130-4 is determined. Alternatively oradditionally, at 2052, the position of the second terminal 130,130-1-130-4 transmitting UL pilot signals 310-318 can be determined withrespect to the first terminal 130, 130-1-130-4 receiving the UL pilotsignals 310-318. E.g., the relative position of the first terminal 130,130-1-130-4 with respect to the second terminal 130, 130-1-130-4 may bedetermined. E.g., the relative position may be defined with respect toone or more eNBs 112, 112-1-112-3. E.g., as part of 2052, the traveltime of the UL pilot signals 310-318 from the second terminal 130,130-1-130-4 to the first terminal 130, 130-1-130-4 can be taken intoaccount. Alternatively or additionally, the angle of arrival can betaken into account. Triangulation techniques may be employed.Alternatively or additionally, the travel time of the UL pilot signals310-318 from the second terminal 130, 130-1-130-4 to the respective eNB112, 112-1-112-3 can be taken into account. Alternatively oradditionally, a travel time of further UL pilot signals 310-318 from thefirst terminal 130, 130-1-130-4 to the respective eNB 112, 112-1-112-3can be taken into account. Positioning based on the UL pilot signals310-318 can be complemented by further positioning techniques; inparticular in such a context it may be favorable if the identities ofall participating terminals 130, 130-1-130-4 are known to fusionpositioning information accurately. Further positioning techniques mayinclude: GPS, compass, gyroscope, pressure sensor; etc. Thus, as can beseen from 2052, it is possible to use power-boosted pilot signals310-318 as positioning beacons.

Thus, as part of 2052, the terminal 130, 130-1-130-4 thatreceives/detects a set of UL pilot signals 310-318 originating fromother terminals 130, 130-1-130-4 can use such information to locallyperform calculations for location information/positioning of the otherterminals 130, 130-1-130-4 in relation to itself. In case the firstterminal 130, 130-1-130-4 receiving the UL pilot signal has informationabout its own position available, e.g., by means of a Global PositioningSystem (GPS) or similar, the first terminal 130, 130-1-130-4 canimplement initial location estimates of the second terminals 130,130-1-130-4. In order to detect the angle of arrival from UL pilotsignals 310-318, multiple antenna reception by MIMO or MAMI techniquescan be employed. Further angle information can complement suchinformation, e.g., by the use of a compass or another sensor. In furtherexamples, such additional data can also be reported by the firstterminal 130, 130-1-130-4 to the eNB 112, 112-1-112-3 as part of the ULreport message 902. The UL report message 902 may be transmitted upon aspecific request or may be pro-actively/autonomously triggered. By suchtechniques, it is possible that the received UL pilot signals 310-318can be combined with further terminal-specific information such as theposition, detected angle of arrival, mobility information, compassinformation, pressure sensor information, etc.; all such information canbe used by the network to further combine with available information toimprove positioning accuracy. E.g., the network may combine severaldifferent UL report messages of terminals 130, 130-1-130-4 to furtherrefine the position estimate. The UL report messages 902 can contain anindicator indicative of the geolocation, e.g., from GPS, and relativeposition information from multiple terminals 130, 130-1-130-4. Thereby,the network and obtain the geolocation/absolute position of the targetterminals 130, 130-1-130-4 in an accurate manner.

A second use-case corresponds to 2053. At 2053, a relay channel isestablished. E.g., the relay channel can between the first terminal 130,130-1-130-4 receiving UL pilot signals 310-318 transmitted by the secondterminal 130, 130-1-130-4 and a respective eNB 112, 112-1-112-3. E.g.,the relay channel can employ the second terminal 130, 130-1-130-4 as arelay. E.g., if the first terminal 130, 130-1-130-4 receives the ULpilot signals 310-318 transmitted by the second terminal 130,130-1-130-4 and, based on the received UL pilot signals 310-318, it isdetermined that a path loss between the second terminal 130, 130-1-130-4and the first terminal 130, 130-1-130-4 is comparably small, it can bejudged that establishing of the relay channel is favorable, e.g., interms of transmission reliability and/or energy consumption.

As an example, at 2053, information obtained from received UL pilotsignals 310-318 can be used to select suitable terminals 130,130-1-130-4 for relay functionality. E.g., a new relay may be selectedfrom a plurality of candidate relays. E.g., the selection of relays maybe based on certain device types such as a particular class of terminals130, 130-1-130-4 defined within the cellular network 100 that arecapable of relaying or acting as a forwarding link of informationbetween a further terminal 130, 130-1-130-4 and an eNB 112, 112-1-112-3.In order to understand which terminals 130, 130-1-130-4 are withinproximity of each other to, thereby, select suitable devices as a relay,the concept of the first terminal 130, 130-1-130-4 receiving UL pilotsignals 310-318 transmitted by at least one second terminal 130,130-1-130-4 as described herein can be employed. In particular,positioning information derived from 2052, as explained above, can betaken into account as part of 2053, as well.

A third use-case corresponds to 2054. At 2054, a sidelink channel isestablished. E.g., the sidelink channel can be between a first terminal130, 130-1-130-4 receiving UL pilot signals 310-318 transmitted by asecond terminal 130, 130-1-130-4. E.g., if the first terminal 130,130-1-130-4 receives the UL pilot signals 310-318 transmitted by thesecond terminals 130, 130-1-130-4 and it is determined that the pathloss between the second terminal 130, 130-1-130-4 and the first terminal130, 130-1-130-4 is comparably small, it can be judged that establishingthe sidelink channel is favorable, e.g., in terms of transmissionreliability and/or energy consumption and/or resource allocation and/ordelay. Hence, it is possible to use power-boosted pilot signals 310-318as D2D discovery signals.

A fourth use-case corresponds to 2055. At 2055, a repetitive resourcemapping for communicating pilot signals 310-318 is determined. E.g., therepetitive resource mapping 301, 301A can be determined such thatresources 305 are shared between two terminals 130, 130-1-130-4communicating pilot signals 310-318. E.g., the repetitive resourcemapping 301, 301A can be determined such that resources 305 are notshared between two terminals 130, 130-1-130-4 communicating pilotsignals 310-318; FDMA, TDMA, and/or CDMA may be employed. E.g., at 2055,a position of the two terminals 130, 130-1-130-4 with respect to eachother can be taken into account; for this, it is possible to rely ontechniques as described above with respect to 2052 and/or furtherpositioning techniques.

As an example, as part of 2055, if there are no UL report messages 902received by the eNB 112, 112-1-112-3 which indicate activity of UL pilotsignals 310-318 in a certain resource, it is likely that this resourceis available for communication of pilot signals 310-318. Inter-cellinterference is not expected in such resources.

In a further example, as part of 2055, if the eNB 112, 112-1-112-3 hasknowledge on the position of the participating terminals 130,130-1-130-4, resources may be re-used for communicating pilot signals310-318 in different parts of a cell where no or only littleinterference is expected. Thus, pilot contamination can be avoided;while, at the same time, resources are efficiently utilized.

A fifth use-case corresponds to 2056. 2056 corresponds to channelsensing. At 2056, a condition of one or more channels 261-263implemented on the radio link 101 are determined. By consideringpower-boosted pilot signals 310-318, more data points can be consideredwhen determining the channel condition. Thus, a highly accurate channelsensing can be employed. In particular, channel sensing may be employedfor a MIMO channel. Typically, operation of communication on a MIMOchannel requires highly-accurate channel sensing. By considering moredata points as described above, such highly-accurate channel sensing canbe implemented. The techniques may find particular application for MAMIscenarios. E.g., MIMO and/or MAMI channel sensing may rely onreciprocity between UL and DL conditions. Often, MAMI scenarios rely onUL pilot signals 310-318, only. In some examples, frequency divisionduplex (FDD) channels may be considered. Here, due to the smallerbandwidth validity/coherence, separate UL and DL pilot signals 310-318may be communicated. Also in a channel having a large bandwidth,multiple pilot signals 310-318 may be communicated at differentfrequencies in order to sound different subbands.

A sixth use-case corresponds to 2057. At 2057, a handover is prepared.E.g., the handover can be between two neighboring cells. It is alsopossible that the handover is between a macro cell and the micro cell.By using power-boosted pilot signals 310-318, advance notice of aterminal 130, 130-1-130-4 approaching a cell edge can be established.Thus, an accurate trigger criterion for executing the handover can betaken into account.

Although the invention has been shown and described with respect tocertain preferred embodiments, equivalents and modifications will occurto others skilled in the art upon the reading and understanding of thespecification. The present invention includes all such equivalents andmodifications and is limited only by the scope of the appended claims.

E.g., while above various examples have been described with respect toUL pilot signals, respective techniques may be readily implemented withrespect to DL pilot signals or sidelink pilot signals.

E.g., while above various examples have been described with respect toE-UTRAN, other RATs can be employed.

E.g., while above various examples have been described with respect areport message indicative of at least one property of a received atleast one uplink pilot signal, similar techniques may be readilyimplemented for a report message indicative of at least one property ofa received at least one downlink pilot signal.

E.g., while above reference has been made to repetitive resourcemappings, in other examples also non-repetitive resource mappings may beemployed.

1. A method, comprising: receiving, by a first terminal, on a radio linkof a cellular network, at least one uplink pilot signal transmitted byat least one second terminal, transmitting by the first terminal, on theradio link and to an access node of the cellular network, an uplinkreport message indicative of at least one property of the received atleast one uplink pilot signal.
 2. A method, comprising: receiving, by anaccess node of a cellular network, on a radio link of the cellularnetwork and from a first terminal, an uplink report message indicativeof at least one property of at least one uplink pilot signal received bythe first terminal, the at least one uplink pilot signal beingtransmitted by at least one second terminal.
 3. The method of claim 1,further comprising: based on the at least one property of the receivedat least one uplink pilot signal, determining a relative position of thefirst terminal with respect to at least one of the at least one secondterminal and the access node.
 4. The method of claim 1, furthercomprising: based on the at least one property of the received at leastone uplink pilot signal: establishing a relay channel between the firstterminal and the access node and via a given one of the at least onesecond terminal as a relay.
 5. The method of claim 1, furthercomprising: based on the at least one property of the received at leastone uplink pilot signal, establishing a sidelink channel between thefirst terminal and a given one of the at least one second terminal. 6.The method of claim 1, further comprising: based on the at least oneproperty of the received at least one uplink pilot signal, determining acondition of a multi-input multi-output, MIMO, channel implemented onthe radio link.
 7. The method of claim 1, further comprising: based onthe at least one property of the received at least one uplink pilotsignal, determining at least one resource mapping for communication ofpilot signals by at least one of the first terminal and the secondterminal.
 8. The method of claim 7, wherein said determining of the atleast one resource mapping is further based on a relative position ofthe first terminal with respect to the at least one second terminal. 9.The method of claim 1, wherein the first terminal receives the at leastone uplink pilot signal in a subset of a sequence of transmissionintervals.
 10. The method of claim 9, further comprising: sporadicallyor persistently scheduling, between the first terminal and the accessnode, the transmission intervals of the subset.
 11. The method of claim9, wherein the at least one uplink pilot signal in the subset of thesequence of transmission intervals has a non-zero second transmit powerand is communicated according to a resource mapping, wherein at leastone further uplink pilot signal in a further subset of the sequence oftransmission intervals has a non-zero first transmit power smaller thanthe second transmit power and is communicated according to the resourcemapping.
 12. The method of claim 11, further comprising: the firstterminal not receiving the at least one further uplink pilot signal. 13.The method of any one of claim 1, wherein the uplink report message isindicative of the at least one property of a plurality of uplink pilotsignals transmitted in a plurality of transmission intervals, whereinthe plurality of uplink pilot signals is optionally transmitted by aplurality of second terminals.
 14. The method of any one of claim 1,wherein the at least one property of the received at least one uplinkpilot signal is selected from the group comprising: an amplitude of thereceived at least one uplink pilot signal, a phase of the received atleast one uplink pilot signal, a resource of the received at least oneuplink pilot signal, a time offset of the received at least one uplinkpilot signal, resource identification information of the received atleast one uplink pilot signal, and an angle of arrival of the receivedat least one uplink pilot signal.
 15. The method of any one of claim 1,wherein the at least one uplink pilot signal is received by the firstterminal during a silent period during which the first terminal does nottransmit on the radio link.
 16. The method of claim 1, wherein the atleast one uplink pilot signal is selected from the group comprising:Sounding Reference Signal, SRS; and Demodulation Reference Signal, DRS.17. The method of claim 1, wherein the uplink report message isindicative of a position of the first terminal.
 18. A terminalconfigured to be attached to a cellular network, the terminalcomprising: an interface configured to transceive on a radio link of thecellular network, at least one processor configured to receive, via theinterface, at least one uplink pilot signal transmitted by at least onefurther terminal, wherein the at least one processor is furtherconfigured to transmit, via the interface and to an access node of thecellular network, an uplink report message indicative of at least oneproperty of the received at least one uplink pilot signal.
 19. An accessnode of a cellular network, comprising: an interface configured totransceive on a radio link of the cellular network, at least oneprocessor configured to receive, via the interface and from a firstterminal, an uplink report message indicative of at least one propertyof at least one uplink pilot signal received by the first terminal, theat least one uplink pilot signal being transmitted by at least onesecond terminal.
 20. A terminal configured to execute operations of themethod of claim 1.